In many countries, the regulations oblige operators to inert unused pipelines as well as any buried tanks. The same applies to dry wells and abandoned wells used in drilling for oil or gas.
The operators of pipeline networks must employ the necessary means so that abandoned or unused pipelines and equipment cannot pose a safety hazards for persons and property.
The purpose of these regulatory requirements is to control the specific hazards that abandoned works may pose to persons or property, owing to:                the possibility of subsidence;        drainage to a building of any gas leak or any other fluids;        potential confusion between works when there are operations in the vicinity.        
When a pipeline of the network is no longer to be used, the network operator is to adopt one of the following arrangements in the order of priority given below:                1) either use it as a sleeve for receiving another pipeline;        2) or abandon it temporarily with a view to later use as a sleeve;        3) or abandon it definitively in the ground. In this case the network operator must make arrangements intended to prevent any subsequent hazards of accident or land subsidence.        
The arrangements to be made for eliminating these hazard are the inerting of pipelines.
“Inerting of abandoned pipelines, tanks or wells” means filling them with an inert substance for said abandoned pipelines, tanks or wells. In general, once filling has been carried out, the open ends are plugged to contain and protect the substance injected.
The pipelines may be:                gas pipes,        pipelines for water (in many cases such as irrigation, there is no such obligation).        
Most often, the operators try to inert the pipelines temporarily and reuse them after variable time periods.
One solution for inerting pipelines consists of filling the pipeline with a slurry of sand. This technique is still difficult to apply because plugs form, preventing propagation of the sand. Moreover, if propagation is forced with high-pressure pumps, filling is incomplete. Finally, it is particularly difficult to unblock pipework with high-pressure pumps, as the pressure required may be greater than the strength of the pipes.
Another solution consists of injecting relatively homogeneous lean concrete using concrete pumps. However, such an operation is only possible over short distances, section by section, as the concrete pumps used for public works have limited pressures. Moreover, the use of high-pressure concrete pumps presents a risk of explosion of the pipelines, which condemns them definitively.
In the case of abandoning and of inerting pipelines in urban areas for example, the inerting operations are very expensive. In fact, to inject lean concrete, it is necessary to open up or drill the ground, roads or sidewalks every 100 or 200 meters. It is not in fact possible to push concrete beyond these distances. Moreover, the equipment for carrying out this drilling is bulky and expensive. Repairing road surfaces damaged during these operations is also expensive and causes a lot of inconvenience for traffic.
Regarding drilling for gas or oil, the regulations apply to dry wells or to abandoned wells.
Very often, dry wells are filled with sand or lean concrete, or partly sand with a concrete covering. For places with difficult access such as frozen lakes or offshore drilling, transport is particularly expensive, requiring the use of helicopters.
Finally, the tanks referred to in the invention are most often at old, disused service stations or are individual buried gas tanks.